For the OP's question......
Simply play the game and put yourself in more tank situations, a FAQ gives an idea of what to do but expierence is the true teacher.
If you find yourself losing aggro in a group, switch to full dps stance and have your hate proc on. This way your doing great dps that builds hate while procing tuants. If healer cant keep up then switch to the tank/dps stance. I rarely use the tank stance any more, even in KoS. Some healers will have trouble at first trying to keep ya healed but they get the hang of it.
THere are so many little tricks our class can do it would honestly take all day to write em all. So go play as a tank more and see if you come up with your own ways. Playing as a tank once then saying you dont know how is fine but maybe playing as tank 2, 3, 100 times might teach you better then any of this chat can. =)
Good Luck